cifs: fix DFS failover

In do_dfs_failover(), the mount_get_conns() function requires the full
fs context in order to get new connection to server, so clone the
original context and change it accordingly when retrying the DFS
targets in the referral.

If failover was successful, then update original context with the new
UNC, prefix path and ip address.
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Cc: stable@vger.kernel.org # 5.11
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/connect.c

@@ -3047,26 +3047,49 @@ static int update_vol_info(const struct dfs_cache_tgt_iterator *tgt_it,
 	return 0;
 }
 
-static int setup_dfs_tgt_conn(const char *path, const char *full_path,
-			      const struct dfs_cache_tgt_iterator *tgt_it,
-			      struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx,
+static int do_dfs_failover(const char *path, const char *full_path, struct cifs_sb_info *cifs_sb,
+			   struct smb3_fs_context *ctx, struct cifs_ses *root_ses,
 			   unsigned int *xid, struct TCP_Server_Info **server,
 			   struct cifs_ses **ses, struct cifs_tcon **tcon)
 {
 	int rc;
+	struct dfs_cache_tgt_list tgt_list = {0};
+	struct dfs_cache_tgt_iterator *tgt_it = NULL;
+	struct smb3_fs_context tmp_ctx = {NULL};
+
+	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
+		return -EOPNOTSUPP;
+
+	cifs_dbg(FYI, "%s: path=%s full_path=%s\n", __func__, path, full_path);
+
+	rc = dfs_cache_noreq_find(path, NULL, &tgt_list);
+	if (rc)
+		return rc;
+	/*
+	 * We use a 'tmp_ctx' here because we need pass it down to the mount_{get,put} functions to
+	 * test connection against new DFS targets.
+	 */
+	rc = smb3_fs_context_dup(&tmp_ctx, ctx);
+	if (rc)
+		goto out;
+
+	for (;;) {
 		struct dfs_info3_param ref = {0};
-	char *mdata = NULL;
-	struct smb3_fs_context fake_ctx = {NULL};
-	char *fake_devname = NULL;
+		char *fake_devname = NULL, *mdata = NULL;
 
-	cifs_dbg(FYI, "%s: dfs path: %s\n", __func__, path);
+		/* Get next DFS target server - if any */
+		rc = get_next_dfs_tgt(path, &tgt_list, &tgt_it);
+		if (rc)
+			break;
 
 		rc = dfs_cache_get_tgt_referral(path, tgt_it, &ref);
 		if (rc)
-		return rc;
+			break;
 
-	mdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options,
-					   full_path + 1, &ref,
+		cifs_dbg(FYI, "%s: old ctx: UNC=%s prepath=%s\n", __func__, tmp_ctx.UNC,
+			 tmp_ctx.prepath);
+
+		mdata = cifs_compose_mount_options(cifs_sb->ctx->mount_options, full_path + 1, &ref,
 						   &fake_devname);
 		free_dfs_info_param(&ref);
 
@@ -3074,69 +3097,41 @@ static int setup_dfs_tgt_conn(const char *path, const char *full_path,
 			rc = PTR_ERR(mdata);
 			mdata = NULL;
 		} else
-		rc = cifs_setup_volume_info(&fake_ctx, mdata, fake_devname);
+			rc = cifs_setup_volume_info(&tmp_ctx, mdata, fake_devname);
 
 		kfree(mdata);
 		kfree(fake_devname);
 
-	if (!rc) {
-		/*
-		 * We use a 'fake_ctx' here because we need pass it down to the
-		 * mount_{get,put} functions to test connection against new DFS
-		 * targets.
-		 */
+		if (rc)
+			break;
+
+		cifs_dbg(FYI, "%s: new ctx: UNC=%s prepath=%s\n", __func__, tmp_ctx.UNC,
+			 tmp_ctx.prepath);
+
 		mount_put_conns(cifs_sb, *xid, *server, *ses, *tcon);
-		rc = mount_get_conns(&fake_ctx, cifs_sb, xid, server, ses,
-				     tcon);
+		rc = mount_get_conns(&tmp_ctx, cifs_sb, xid, server, ses, tcon);
 		if (!rc || (*server && *ses)) {
 			/*
-			 * We were able to connect to new target server.
-			 * Update current context with new target server.
+			 * We were able to connect to new target server. Update current context with
+			 * new target server.
 			 */
-			rc = update_vol_info(tgt_it, &fake_ctx, ctx);
-		}
-	}
-	smb3_cleanup_fs_context_contents(&fake_ctx);
-	return rc;
-}
-
-static int do_dfs_failover(const char *path, const char *full_path, struct cifs_sb_info *cifs_sb,
-			   struct smb3_fs_context *ctx, struct cifs_ses *root_ses,
-			   unsigned int *xid, struct TCP_Server_Info **server,
-			   struct cifs_ses **ses, struct cifs_tcon **tcon)
-{
-	int rc;
-	struct dfs_cache_tgt_list tgt_list;
-	struct dfs_cache_tgt_iterator *tgt_it = NULL;
-
-	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
-		return -EOPNOTSUPP;
-
-	rc = dfs_cache_noreq_find(path, NULL, &tgt_list);
-	if (rc)
-		return rc;
-
-	for (;;) {
-		/* Get next DFS target server - if any */
-		rc = get_next_dfs_tgt(path, &tgt_list, &tgt_it);
-		if (rc)
-			break;
-		/* Connect to next DFS target */
-		rc = setup_dfs_tgt_conn(path, full_path, tgt_it, cifs_sb, ctx, xid, server, ses,
-					tcon);
-		if (!rc || (*server && *ses))
+			rc = update_vol_info(tgt_it, &tmp_ctx, ctx);
 			break;
 		}
+	}
 	if (!rc) {
+		cifs_dbg(FYI, "%s: final ctx: UNC=%s prepath=%s\n", __func__, tmp_ctx.UNC,
+			 tmp_ctx.prepath);
 		/*
-		 * Update DFS target hint in DFS referral cache with the target
-		 * server we successfully reconnected to.
+		 * Update DFS target hint in DFS referral cache with the target server we
+		 * successfully reconnected to.
 		 */
-		rc = dfs_cache_update_tgthint(*xid, root_ses ? root_ses : *ses,
-					      cifs_sb->local_nls,
-					      cifs_remap(cifs_sb), path,
-					      tgt_it);
+		rc = dfs_cache_update_tgthint(*xid, root_ses ? root_ses : *ses, cifs_sb->local_nls,
+					      cifs_remap(cifs_sb), path, tgt_it);
 	}
+
+out:
+	smb3_cleanup_fs_context_contents(&tmp_ctx);
 	dfs_cache_free_tgts(&tgt_list);
 	return rc;
 }